GS2971 Datasheet, PDF (88/148 Pages) Semtech Corporation – 3Gb/s, HD, SD SDI Receiver, with Integrated Adaptive Cable Equalizer complete with SMPTE Audio and Video Processing

The audio buffer pointer offset may be reduced from 26 samples to 12 or 6 samples using
the OS_SEL[1:0] bits in the host interface. The default setting is 26 samples (see
Table 4-21).
When the OS_SEL[1:0] bits are set for 6-sample pointer offset, no boundary-checking is
performed.
In HD mode the audio FIFO is a maximum of 10 samples deep. According to SMPTE
299M, audio samples are multiplexed immediately in the next HANC region after the
audio sample occurs.
Table 4-21: Audio Buffer Pointer Offset Settings
OS_SEL[1:0]
00
01
10
Buffer Pointer Offset
26 samples (default)
12 samples
6 samples
4.19.3.4 Audio Crosspoint Block
The Audio Crosspoint is used for audio output channel re-mapping. This feature allows
any of the selected audio channels in Group A or Group B to be output on any of the eight
output channels. The default setting is for one to one mapping, where AOUT_1/2 is
extracted from Group A CH1 and CH2, AOUT_3/4 is extracted from Group A CH3 and
CH4, and so on.
NOTE: If audio samples from embedded audio packets with the group set in IDA[1:0] are
to be paired with samples from the group set in IDB[1:0], all of the channels must have
been derived from the same Word Clock and must be synchronous.
The output channel is set in the OPn_SRC[2:0] host interface registers. Table 4-22 lists the
3-bit address for audio channel mapping.
Table 4-22: Audio Channel Mapping Codes
Audio Output Channel
1
2
3
4
5
6
7
8
3-bit Host Interface
Source Address
000
001
010
011
100
101
110
111
GS2971 3Gb/s, HD, SD SDI Receiver
Data Sheet
45898 - 2
September 2012
88 of 148